Basic Research| Volume 47, ISSUE 9, P1427-1434, September 2021

Download started.


Fibroblasts Control Macrophage Differentiation during Pulp Inflammation



      During pulp inflammation, recruited macrophages can differentiate into 2 phenotypes: proinflammatory M1 and anti-inflammatory M2. Pulp fibroblasts have previously been shown to regulate pulp inflammation via cytokine and growth factor secretion. We hypothesized that upon carious injury, pulp fibroblasts interact with macrophages and modulate their differentiation.


      Cultures of pulp fibroblasts were physically injured and incubated with lipoteichoic acid (LTA) to mimic the pulp environment underlying a carious lesion. Physical injuries without LTA were performed on cultured fibroblasts to simulate the surrounding pulp tissue. Fibroblast supernatants were collected and added to undifferentiated macrophages to study their differentiation into M1 or M2 phenotypes by investigating cytokine secretion profiles and phagocytosis capacity. Histologic staining and immunofluorescence were performed on healthy and carious human tooth sections to localize the 2 macrophage phenotypes.


      LTA-stimulated fibroblasts induced macrophage differentiation into the M1 phenotype with a significant increase both in tumor necrosis factor alpha secretion and phagocytosis capacity. By contrast, injured fibroblasts without LTA led to M2 differentiation with a significant increase in interleukin 10 secretion and low phagocytosis capacity. In carious teeth, M1 macrophages were detected mainly in the pulp zone underlying caries, whereas M2 macrophages were detected in the peripheral inflammatory zone.


      Fibroblasts induced macrophage differentiation to proinflammatory M1 with high bacteria phagocytosis capacity to control infection at the carious front. Fibroblasts located at the periphery of the inflammatory zone induced macrophage differentiation to anti-inflammatory M2. The fine balance between the 2 phenotypes may represent a prerequisite for initiating the healing process.

      Key Words

      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Journal of Endodontics
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Farges J.C.
        • Alliot-Licht B.
        • Renard E.
        • et al.
        Dental pulp defence and repair mechanisms in dental caries.
        Mediators Inflamm. 2015; 2015: 1-16
        • Giraud T.
        • Jeanneau C.
        • Bergmann M.
        • et al.
        Tricalcium silicate capping materials modulate pulp healing and inflammatory activity in vitro.
        J Endod. 2018; 44: 1686-1691
        • Yumoto H.
        • Hirao K.
        • Hosokawa Y.
        • et al.
        The roles of odontoblasts in dental pulp innate immunity.
        Jpn Dent Sci Rev. 2018; 54: 105-117
        • Farges J.C.
        • Keller J.F.
        • Carrouel F.
        • et al.
        Odontoblasts in the dental pulp immune response.
        J Exp Zool B Mol Dev Evol. 2009; 312B: 425-436
        • Giraud T.
        • Rufas P.
        • Chmilewsky F.
        • et al.
        Complement activation by pulp capping materials plays a significant role in both inflammatory and pulp stem cells' recruitment.
        J Endod. 2017; 43: 1104-1110
        • Nakakura-Ohshima K.
        Possible role of immunocompetent cells and the expression of heat shock protein-25 in the process of pulpal regeneration after tooth injury in rat molars.
        J Electron Microsc (Tokyo). 2003; 52: 581-591
        • Zhang J.
        The existence of CD11c+ sentinel and F4/80+ interstitial dendritic cells in dental pulp and their dynamics and functional properties.
        Int Immunol. 2006; 18: 1375-1384
        • Martinez F.O.
        Macrophage activation and polarization.
        Front Biosci. 2008; 13: 453
        • Mantovani A.
        • Sica A.
        • Sozzani S.
        • et al.
        The chemokine system in diverse forms of macrophage activation and polarization.
        Trends Immunol. 2004; 25: 677-686
        • Novak M.L.
        • Koh T.J.
        Macrophage phenotypes during tissue repair.
        J Leukoc Biol. 2013; 93: 875-881
        • Nakanishi T.
        • Takahashi K.
        • Hosokawa Y.
        • et al.
        Expression of macrophage inflammatory protein 3alpha in human inflamed dental pulp tissue.
        J Endod. 2005; 31: 84-87
        • Adachi T.
        • Nakanishi T.
        • Yumoto H.
        • et al.
        Caries-related bacteria and cytokines induce CXCL10 in dental pulp.
        J Dent Res. 2007; 86: 1217-1222
        • Cooper P.R.
        • Takahashi Y.
        • Graham L.W.
        • et al.
        Inflammation-regeneration interplay in the dentine-pulp complex.
        J Dent. 2010; 38: 687-697
        • Park H.C.
        • Quan H.
        • Zhu T.
        • et al.
        The effects of M1 and M2 macrophages on odontogenic differentiation of human dental pulp cells.
        J Endod. 2017; 43: 596-601
        • Takei E.
        • Shigetani Y.
        • Yoshiba K.
        • et al.
        Initial transient accumulation of M2 macrophage–associated molecule-expressing cells after pulpotomy with mineral trioxide aggregate in rat molars.
        J Endod. 2014; 40: 1983-1988
        • Yoshiba N.
        • Edanami N.
        • Ohkura N.
        • et al.
        M2 phenotype macrophages colocalize with Schwann cells in human dental pulp.
        J Dent Res. 2020; 99: 329-338
        • Humeres C.
        • Vivar R.
        • Boza P.
        • et al.
        Cardiac fibroblast cytokine profiles induced by proinflammatory or profibrotic stimuli promote monocyte recruitment and modulate macrophage M1/M2 balance in vitro.
        J Mol Cell Cardiol. 2016; 101: 69-80
        • Chmilewsky F.
        • Jeanneau C.
        • Laurent P.
        • About I.
        Pulp fibroblasts synthesize functional complement proteins involved in initiating dentin-pulp regeneration.
        Am J Pathol. 2014; 184: 1991-2000
        • Coil J.
        • Tam E.
        • Waterfield J.D.
        Proinflammatory cytokine profiles in pulp fibroblasts stimulated with lipopolysaccharide and methyl mercaptan.
        J Endod. 2004; 30: 88-91
        • Le Fournis C.
        • Hadjichristou C.
        • Jeanneau C.
        • About I.
        Human pulp fibroblast implication in phagocytosis via complement activation.
        J Endod. 2019; 45: 584-590
        • Tran-Hung L.
        • Mathieu S.
        • About I.
        Role of human pulp fibroblasts in angiogenesis.
        J Dent Res. 2006; 85: 819-823
        • Chmilewsky F.
        • About I.
        • Chung S.H.
        Pulp fibroblasts control nerve regeneration through complement activation.
        J Dent Res. 2016; 95: 913-922
        • Jeanneau C.
        • Lundy F.T.
        • El Karim I.A.
        • About I.
        Potential therapeutic strategy of targeting pulp fibroblasts in dentin-pulp regeneration.
        J Endod. 2017; 43: S17-S24
        • Cooper P.R.
        • Smith A.J.
        Molecular mediators of pulp inflammation and regeneration.
        Endod Topics. 2013; 28: 90-105
        • Al Natour B.
        • Lundy F.T.
        • Moynah P.N.
        • et al.
        Odontoblast cell death induces NLRP3 inflammasome-dependent sterile inflammation and regulates dental pulp cell migration, proliferation and differentiation.
        Int Endod J. 2021; 54: 941-950
        • Rufas P.
        • Jeanneau C.
        • Rombouts C.
        • et al.
        Complement C3a mobilizes dental pulp stem cells and specifically guides pulp fibroblast recruitment.
        J Endod. 2016; 42: 1377-1384
        • Tsuchiya S.
        • Yamabe M.
        • Yamaguchi Y.
        • et al.
        Establishment and characterization of a human acute monocytic leukemia cell line (THP-1).
        Int J Cancer. 1980; 26: 171-176
        • Murray P.J.
        • Allen J.E.
        • Biswas S.
        • et al.
        Macrophage activation and polarization: nomenclature and experimental guidelines.
        Immunity. 2014; 41: 14-20
        • Laroux F.S.
        • Romero X.
        • Wetzler L.
        • et al.
        Cutting edge: MyD88 controls phagocyte NADPH oxidase function and killing of gram-negative bacteria.
        J Immunol. 2005; 175: 5596-5600
        • Téclès O.
        • Laurent P.
        • Zygouritsas S.
        • et al.
        Activation of human dental pulp progenitor/stem cells in response to odontoblast injury.
        Arch Oral Biol. 2005; 50: 103-108
        • Tan H.Y.
        • Wang N.
        • Man K.
        • et al.
        Autophagy-induced RelB/p52 activation mediates tumour-associated macrophage repolarisation and suppression of hepatocellular carcinoma by natural compound baicalin.
        Cell Death Dis. 2015; 6: e1942
        • Chávez-Galán L.
        • Ocaña-Guzmán R.
        • Torre-Bouscoulet L.
        • et al.
        Exposure of monocytes to lipoarabinomannan promotes their differentiation into functionally and phenotypically immature macrophages.
        J Immunol Res. 2015; 2015: 984973
        • Neves V.C.
        • Yianni V.
        • Sharpe P.T.
        Macrophage modulation of dental pulp stem cell activity during tertiary dentinogenesis.
        Sci Rep. 2020; 10: 20216
        • Porcheray F.
        • Viaud S.
        • Rimaniol A.C.
        • et al.
        Macrophage activation switching: an asset for the resolution of inflammation.
        Clin Exp Immunol. 2005; 142: 481-489
        • Benoit M.
        • Desnues B.
        • Mege J.L.
        Macrophage polarization in bacterial infections.
        J Immunol. 2008; 181: 3733-3739